Generators generate power constantly. Scaling is based purely on volume. Required as a ship scales or techs up, as the default generation won't cover stronger ships' power demands.
This block has 4/3rds the mass and 1/8th the durability.
MW/kM³ = 1.875*tier² + 5.625*tier + 75 = 1.875 (40 + 3 tier + tier²)
|HP||Weight (t)||Power (GW)||GW/kt||MW/kM³|
Judging from the chart it is most efficient to use Trinium, as it has the least mass, yielding the best maneuverability, and the most system upgrade slots for the same amount of generated power and volume.